UDBMS A Database System for Managing ConstantlyEvolving Data

U-DBMS: A Database System for Managing Constantly-Evolving Data (VLDB 2005) Reynold Cheng csckcheng@comp. polyu. edu. hk Hong Kong Polytechnic University Sarvjeet Singh, Sunil Prabhakar {singh 35, sunil}@cs. purdue. edu Purdue University Reynold cheng

Sensor Databases sensor Database System sensor External Environment e. g. , temperature, Uncertainty (e. g. , sampling Network moving objects, error) can render incorrect Channel hazardous materials query results. queries results sensor user R. Cheng, S. Singh, S. Prabhakar U-DBMS sensor

Uncertainty Management uncertainty pdf Uncertainty of a Sensor Data Value [L n n uncertainty interval R] Probabilistic Queries: answers with probability Example: Which item, A and B, is smaller? ¡ {(A, 0. 8), (B, 0. 2)} ¡ A correct (possibly less precise) answer, instead of a potentially incorrect answer R. Cheng, S. Singh, S. Prabhakar U-DBMS

U-DBMS Prototype n n n Uncertainty-Data Base Management System Meta-queries for specifying uncertainty interval and type of uncertainty pdf Extension of SQL for probabilistic queries Measurement of query quality Implemented on Postgre. SQL 8. 0 R. Cheng, S. Singh, S. Prabhakar U-DBMS

Architecture of U-DBMS Postgre. SQL 8. 0 R. Cheng, S. Singh, S. Prabhakar U-DBMS

Example Queries Create a table with UNCERTAIN type CREATE table T( k INTEGER primary key, a UNCERTAIN); Insert Gaussian pdf (μ, σ) Insert into T values (1, ‘(g, μ, σ)’); Display uncertain info. of a if a > 5 SELECT a FROM T where a > 5; Equality join of uncertain attributes (=% returns probability of equality) SELECT R. k, S. k, R. a =% S. a FROM R, S WHERE R. a = S. a; Entities with prob. giving min value of a (e. g. , {(3, 0. 5), (5, 0. 3), (11, 0. 2)}) SELECT Emin(T. a) from T; Min value of a for table T (UNCERTAIN) SELECT Vmin(T. a) from T; Reynold cheng U-DBMS